This application is a Continuation-In-Part of Ser. No. 854,907, filed Apr. 23, 1986, now abandoned, which in turn is a divisional of Ser. No. 745,520, now abandoned, filed June 17, 1985.
(1) Field of the Invention
This invention relates to an emergency lock retractor equipped with a webbing clamp device, which has such a function that its emergency lock mechanism is held inoperative while no emergency locking is required.
(2) Description of the Prior Art
An emergency lock retractor serves to detect a sudden speed change of its associated vehicle or a sudden release of its webbing to prevent any further rotation of its take-up spindle, thereby preventing any further release of the webbing. Even with this emergency lock retractor, the webbing is tightened up further when a still stronger tensile force is applied to the webbing owing to the inertia of the occupant subsequent to the actuation of its locking mechanism in the event of an emergency. The webbing is thus allowed to extend forward together with the occupant, leading to a failure in safely restraining the occupant.
With a view toward overcoming such a problem, emergency lock retractors equipped with webbing clamp devices have been proposed. According to an emergency lock retractor equipped with a webbing clamp device, its webbing is held by a clamp device subsequent to actuation of its emergency lock mechanism so as to exert a brake force against movement of the webbing in the webbing releasing direction, whereby to prevent any further release of the webbing which otherwise takes place due to tightening of the webbing.
In the above-mentioned emergency lock retractor equipped with such a webbing clamp device, the webbing is rapidly taken up on a take-up reel owing to the biasing force of a take-up spring when the occupant has stopped using the seat belt and released the webbing from his hand. Here, the take-up reel may be caused to over-rotate beyond the prescribed winding end position due to the inertia. When the emergency lock mechanism has been actuated by a vibration of its associated vehicle or the like in such an over-rotated state, for example, when a sensor arm has been caused to swing into engagement with a ratchet gear mounted fixedly on a take-up spindle, the take-up reel starts backward rotation to the prescribed winding position. This backward rotation of the take-up reel urges the ratchet gear and sensor arm in such a way that they maintain their engagement (in other words, in the webbing releasing direction), thereby freezing the emergency lock state (this state will hereinafter be called "the end lock state").
In the case of an emergency lock retractor equipped with no webbing clamp device, the wound webbing is tightened and is thus released when the webbing is pulled by a large force. By winding back the thus-released webbing, the take-up spindle is allowed to rotate in the winding direction. It is therefore possible to release the emergency lock mechanism from the end lock state. It is however impossible to release an emergency lock retractor equipped with a webbing clamp device from the end lock state, because owing to the provision of the webbing clamp device preventing the tightening of the wound webbing subsequent to its emergency locking, the webbing clamp device is actuated to hold and lock the webbing when the webbing is pulled strongly subsequent to the development of the end lock state and it is thus unable to tighten the wound webbing and to wind back the webbing over a length equivalent to the length released by its tightening. Once the emergency lock retractor equipped with the webbing clamp device has been brought into the end lock state, it becomes absolutely impossible to pull out the webbing and unless the webbing clamp device is provided with a mechanism capable of forcedly releasing the clamping of the webbing clamp device, the seat belt system thus becomes no longer usable.